Silver halide emulsions having chill-setting properties



' etc.

sea plants of certain types which extractives are readily United States Patent 3,250,620 SILVER HALIDE EMULSIONS HAVING CHILL-SETTING PROPERTIES William G. Lovett and David B. Fogg, Rochester, N.Y.,

assignors .to Eastman Kodak Company, Rochester,

N.Y., a corporation of New Jersey No Drawing. Filed Jan. 18, 1962, Ser. No. 167,150

4 Claims. (Cl. 96-94) This invention relates to the incorporation of carrageenans into grain-washed silver halide photographic emulsion to'improve their chill-setting properties and to increase the carrying characteristics of the gelatin.

Probably the best known silver halide photographic emulsions at the present time are those in which silver halide is carried by a gelatin vehicle. As photographic emulsions are ordinarily coated out onto a support which involves chill-setting and drying, it has been desirable to have a concentration of at least 4% gelatin in the emulsion composition to obtain firm gelling of the coating in the chill-setting operation.

Sometimes, it is desirable to have photographic emulsions in which the coatings contain smaller proportions of gelatin than 4% so as. to obtain thin coatings. However, because of the 4% minimum of gelatin required for good chill-setting, this has created a problem particularly in the use of conventional coating hoppers.

One object of our invention is to make possible the preparation of grain-washed photographic emulsions having good physical properties in which concentrations of gelatin or other vehicle such as on the order of 1 or 2% may be used. Another object of our invention is to provide photographic emulsions which quickly chill-set after coating upon applying cooling thereto. A still further object of our invention is to provide photographic emulsions in which carrageenans are present to improve carrying and chill-setting properties. invention will appear herein.

We have found that the chill-setting rates of grainwashed silver halide photographic emulsions can be improved by incorporating in those compositions carrageenans in a porportion in the range of 1.0 to 100% based on the weight of the colloidal material the colloidal material being at a concentration of 0.1 to 6% and more especially 0.1 to 2%. We have found that these materials are compatible over a wide range with normal lime-processed gelatins, with gelatin derivatives useful for grain wash processes as disclosed in US. Patent No. 2,525,753 of Yutzy et al., with low viscosity gelatins, graft polymers, These carrageenans are obtained by extracting red soluble in water and mix readily with photographic emulsions to impart increased viscosity characteristics and improved chill-setting rates when mixed therewith.

The carrageenans are principally prepared from sea plants known as Chondrus crispus and Gigartina' mamz'llosa (Irish moss). These extractives appear to be alkali metal salts of a sulfuric acid ester of a carbohydrate polymer having a molecular weight of at least 20,000. Some of the plants which give carrageenan extractives are the following:

Aeodes orbitosa Chondrus canalicu'latus Chondrus ocellatus Eucheuma cottonil Eucheuma edule Eztcheuma murz'catus Gigartina accularis Gigartina asperifolia Gigartina canaliculata Gigartina decipiens Other objects of our 3,250,620 Patented May 10, 1 966 ice The extractives which are useful in accordance with our invention are the higher molecular weight extractives having good chill-setting properties. The useful extractives have been found to be uniformly of a molecular weight greater than 20,000. Useful extractives are marketed commercially under names such as Pencogel, by the Penick Company; and SeaKem extractives, by Seaplant Corporation, New Bedford, Massachusetts. These extractives while improving the chill-setting properties of the gelatin, gelatin derivatives or colloidal materials used for silver halide carriers in the manufacture of photographic emulsions and increasing the viscosity properties thereof, do not exhibit any detrimental effect upon the photographic emulsions in which they are incorporated.

The colloidal materials whose properties are improved by mixing with a carrageenan are those whose aqueous dispersions are recognized as useful as vehicles for the silver halide in photographic emulsions. Included are not only gelatins of various kinds such as normal and low viscosity gelatins, glues, pigmented gelatins, and gelatin derivatives butother colloidal materials such as graft polymers which form hydrosols useful for preparing photographic emulsions for example those described in US. Patents Nos. 2,763,625 and 2,787,545.

Our invention comprises adding extractive of higher molecular weight to a grain-washed silver halide photographic emulsion, in the preparation of which the silver halide grains, prepared by reacting AgNO and alkali metal halide, are washed such as by the grain-washing procedure described in Yutzy et a1. Patents Nos. 2,614,- 928 and 2,614,929, by a salting out process or by some equivalent procedure. The washed silver halide grains are then mixed with a protective colloid such as gelatin and any other additives to impart desire-d photographic properties thereto. The extractive is added to the photographic emulsion at any time prior to coating out as a layer upon a support therefor. As certain acid pHs such as 3.5 or lower or some oxidizing agents such as hypochlorite or peroxides have a degrading effect upon these extractives, it is advisable to avoid treatments of this kind of compositions containing the carrageenans.

The following examples illustrate the use of this material in photographic emulsions:

Example I A moderate speed grain-washed gelatin-silver bromoiodi-de emulsion was digested and optically sensitized which emulsion contained a cyan dye forming coupler dispersed in a high boiling organic solvent. The emulsion was divided into several .parts and each portion was coated onto a support. Various proportions of high molecular weight extractives as referred to were added which addition increased the viscosity of the gelatin vehicle of the emulsion. The coatings obtained were exposed for ,6 sec. to the light emitted by a 500 watt tungsten lamp in an intensity scale sensitometer and the exposed emulsion layers were processed in a suitable color processing operation. It is found that even though various concentrations of extractives were used, the emulsion speeds were unaffected by the presence of extractive therein. The addition of extractive increased the chill-setting properties and viscosities of the various emulsions tacilitating coating operations.

Example 2 A high speed grain-washed silver bromoiodide photographic emulsion was prepared having a gelatin concen tration of 1% and 0.33% of high molecular weight carrageenan. This emulsion was coated upon cellulose acetate film support and was placed on a block chilled by 40 F. water. The coating set firmly in 25 seconds. A similar emulsion having a gelatin concentration of 1.3% and no carrageenan or the like showed no chill-setting when coated and chilled under the conditions described.

Example 3 A solution was prepared having a 5% concentration of a graft polymer made by the process of US. Patent No. 2,763,625 using 25 parts ethoxyethyl acrylate, 25 parts acrylic acid and 50 parts of bone gelatin and 05% concentration of high molecular weight carrageenan. The solution was coated on a glass plate and was placed on a block chilled by 40 F. water. The coating set firmly in 25 seconds. Without the carrageenan 4'minutes was required to obtain setting under the described conditions.

We claim:

1. A grain-washed silver halide photographic emulsion having good chill-setting properties comprising grainwashed silver halide grains and a protective colloid, the latter being present in the emulsion in-0.'16% concentration containing therein l.0100%, based on the weight of said protective colloid, of a carrageenan having a molecular weight greater than 20,000.

2. A grain-washed silver halide photographic emulsion having good chill-setting properties comprising grainwashed silver halide grains and a water-soluble gelatinous material as the protective colloid, the latter being present in the emulsion in 0.1-6% concentration containing therein 1.0-l00%, based on the weight of the gelatinous material, of a carrageenan having a molecular weight greater than 20,000.

3. A grain-washed silver halide-gelatin photographic emulsion, the gelatin being present in the emulsion in 0.1-6% concentration containing therein 1.0-%, based on the weight of the gelatin of a carrageenan having a molecular weight greater than 20,000.

4. A grain-washed silver halide photographic emulsion having good chill-setting properties comprising grainwashed silver halide grains and a protective colloid, the latter being present in the emulsion in 0.12% concentration containing therein 1.0100%, based on the weight of the colloidal material of a carrageenan having a molec ular weight greater than 20,000.

References Cited by the Examiner UNITED STATES PATENTS 2,899,327 8/1959 Christopher et al. 106-125 2,933,406 4/1960 Salzberg et al. 106-125 2,952,559 9/1960 Nadeau 117-34 3,026,202 3/1962 Knox et al. 96-94 3,061,453 10/1962 Rogers 117-34 3,068,101 12/1962 Knox et al. 96-94 3,153,594 10/1964 Oberth 96-94 3,184,311 5/1965 Salminen 96-94 NORMAN G. TORCHIN, Primary Examiner.

A. D. RICC I, Assistant Examiner. 

1. A GRAIN-WASHED SILVER HALID PHOTOGRPHIC EMULSION HAVING GOOD CHILL-SETTING PROPERTIES COMPRISING GRAINWASHED SILVER HALIDE GRAINS AND A PROTECTIVE COLLOID, THE LATTER BEING PRESENT IN THE EMULSION IN 0.1-6% CONCENTRATION CONTAINING THEREIN 1.0-100%, BASED ON THE WEIGHT OF SAID PROTECTIVE COLLOID, OF A CARRAGEENAN HAVING A MOLECULAR WEIGHT GREATER THAN 20,00. 